Supramolecular Monitoring Of Conformation And Aggregation/disaggregation Of Melittin In Aqueous Solution

Melittin is provided to have applications in anti-bacterial, anti-inflammatory, anti-radiation and anti-arthritis, particularly, it is also discovered that melittin has ability in anti-tumor and anti-human immunodeficiency virus (HIV). The aggregation and/or conformational changes of melittin are very important to its clinical application. Based on the above background, the present study carries out two parts of researches: (1) supramolecular monitoring of aggregation / disaggregation of melittin in different mediums and the corresponding mechanism study; (2) the adsorption and conformational changes of melittin on the surface of functionalized gold nanoparticles.Firstly, in different media with DOPC, NaCl and/or HP-β-CD, monitoring of aggregation / disaggregation and conformational changes of melittin have been performed. The results show that melittin can combine with DOPC strongly as a monomer inα-helix; in the presence of NaCl, a tetramer inα-helix of melittin can be formed itself; in addition, in the presence of HP-β-CD these two trends have been slowdown. Such studies will be very useful in monitoring the aggregation / disaggregation of protein and further to their application in clinic.Secondly, gold nanoparticles are coated with different chain lengths of sulphydryl carboxylate (MPA and MUA), and finally ones with negative charge have been achieved. As six positive charges covering at the surface of melittin, the functionalized gold nanoparticles and melittin can interact with each other via static interaction in aqueous solution. The present paper has studied the interaction between the functionalized gold nanoparticles and melittin by using multiple spectroscopic means. The results show that the functionalized gold nanoparticles induced melittin to formα-helix by electrostatic interactions, and it is directly related with the chain length of the functional group. In the current experimental conditions, the conversion rate of melittin from random coil toα-helix is improved from 16.7 % to 23.1% induced by MUA-GNPs, which will provide the exploration of the further application of functionalized gold nanoparticles.